I think because I'm a programmer I rely less on spellcheck than non-programmers, because what I write is full of words mashed together as one (spellcheck if flagged by Firefox's spell checker (and BTW the "if" in "spellcheck if" wasn't flagged by anything)), and words that just aren't words (ngninx). I don't usually add those words to the dictionary, because I'm afraid of writing to a non-programmer and having something pass through that shouldn't.
I treat spellcheck as a real-time shoulder sirfer (surfer), and I generally hit Reply/Send/Make-it-so even though my messages are full of wavy red lines.
The errors I saw (before giving up) would not be caught by a spell check. I'll go so far as guessing that a blind spell check was run, with no human check on the corrections.
Or English isn't their first language. That was my impression. Granted, I bailed partly because of the grammar, too but that was after realizing it was a mixed list of soft skills, not algorithms or tools or whatever. Once it wasn't what I expected, the writing didn't help keep me.
I treat spellcheck as a real-time shoulder sirfer (surfer), and I generally hit Reply/Send/Make-it-so even though my messages are full of wavy red lines.